Zone selective interlocking test method and apparatus, and circuit interrupter apparatus and power distribution system including the same

ABSTRACT

A circuit interrupter apparatus includes circuit interrupter and a device. The circuit interrupter includes separable contacts, an operating mechanism structured to open and close the separable contacts, and a trip mechanism cooperating with the operating mechanism to trip open the separable contacts. The trip mechanism includes a zone selective interlocking input and a zone selective interlocking output. The device includes a first input electrically interconnected with the zone selective interlocking input, a second input electrically interconnected with the zone selective interlocking output, and an indicator circuit structured to indicate that the zone selective interlocking input occurred at the first input or that the zone selective interlocking output occurred at the second input.

BACKGROUND

1. Field

The disclosed concept pertains generally to zone selective interlockingand, more particularly, to zone selective interlocking test methods. Thedisclosed concept also pertains to zone selective interlocking testapparatus. The disclosed concept further pertains to circuitinterrupters and power distribution systems including circuitinterrupters.

2. Background Information

Circuit interrupters, such as for example and without limitation,circuit breakers, are used to protect electrical circuitry from damagedue to an overcurrent condition, such as an overload condition, a shortcircuit, or another fault condition, such as an arc fault or a groundfault. Molded case circuit breakers typically include a pair ofseparable contacts per phase. The separable contacts may be operatedeither manually by way of a handle disposed on the outside of the caseor automatically in response to a detected fault condition. Typically,such circuit breakers include an operating mechanism, which is designedto rapidly open and close the separable contacts, and a trip mechanism,such as a trip unit, which senses a number of fault conditions to tripthe breaker automatically. Upon sensing a fault condition, the trip unittrips the operating mechanism to a trip state, which moves the separablecontacts to their open position.

Zone selective interlocking (ZSI) (e.g., also known as “zoneinterlocking”) is a method of controlling circuit breakers in order toprovide selectivity with relatively very short delay times, irrespectiveof the number of zones (e.g., without limitation, a line side zone; aload side zone; a number of upstream zones; a number of downstreamzones; a number of grading levels) and the location of a fault in apower distribution system. A ZSI input and a ZSI output are provided ateach circuit breaker. Interlocking may be applied to faults betweenphases or earth-faults or both.

As one example, zone interlocking uses a communication scheme to connectline and load circuit breaker trip units together. When a fault occurs,the trip units communicate to determine which load side circuit breakeris closest to the fault. The trip unit in the circuit breaker closest tothe fault overrides any customer-defined delay and opensinstantaneously, thereby clearing the fault and allowing the line sidecircuit breakers to remain closed.

If ZSI is used in several zones, then each circuit breaker affected by,for example, a short circuit current (i.e., upstream of the fault)interrogates the circuit breaker(s) directly downstream of that affectedcircuit breaker to determine whether the short circuit current ispresent in or is affecting the adjacent downstream zone. A delay settingt_(ZSI) is adjusted at each circuit breaker to ensure that thedownstream circuit breaker, directly upstream of the fault, has time tointerrupt the fault current. The advantages of ZSI increase withadditional zones, since time-based selectivity can result inunacceptably long delays at the upstream power source end of the system.

Several examples of the operation of ZSI are discussed in connectionwith FIG. 1, which shows an example power distribution system usingmultiple power sources in the upstream ZONE 1. In this example, thereare two downstream zones, ZONE 2 and ZONE 3, although any suitablenumber of downstream zones can be employed. As a first example, there isa fault, such as a short circuit, at position 3. Circuit breakers CB1,CB2, CB3, CB5 and CB7 detect the short circuit. CB7 blocks CB5 by theZSI OUT signal of CB7 and, as a result, also CB1, CB2 and CB3, in orderthat they do not trip for t_(ZSI)=50 ms. Since CB7 does not receive ablocking ZSI IN signal from a subordinate, downstream circuit breaker,CB7 is responsible for interrupting the short circuit as quickly aspossible. In the event of a problem with circuit breaker CB7 (e.g.,because CB7 is no longer operational), then upstream CB5, as a back-up,trips after its short time delay setting, t_(SD)=150 ms.

As a second example, there is a short circuit at position 2. Circuitbreakers CB1, CB2, CB3 and CB5 detect the short circuit, but CB7 doesnot. For this reason, CB5 does not receive a blocking ZSI IN signal fromCB7, but provides a blocking ZSI OUT signal to CB1, CB2 and CB3. Thisinformation tells CB5 that it is the closest breaker upstream of theshort circuit. CB5 trips with a delay of t_(ZSI)=50 ms instead of with adelay of t_(SD)=150 ms. Here, the clearance time is reduced by 100 ms(=t_(SD)−t_(ZSI)=150 ms−50 ms).

As a third example, there is a short circuit at position 1. Only circuitbreakers CB1, CB2 and CB3 detect the short circuit and they do notreceive a blocking ZSI IN signal from any circuit breaker at asubordinate, downstream zone. For this reason, CB1, CB2 and CB3 tripafter t_(ZSI)=50 ms. Here, the time saved is 250 ms (=t_(SD)−t_(ZSI)=300ms−50 ms).

There is no known system to fully test and properly verify a zoneselective interlocking system.

There is room for improvement in zone selective interlocking.

There is also room for improvement in circuit interrupters and powerdistribution systems including circuit interrupters, which employ zoneselective interlocking.

SUMMARY

These needs and others are met by embodiments of the disclosed concept,which provide a device comprising: a first input electricallyinterconnected with a zone selective interlocking input, a second inputelectrically interconnected with a zone selective interlocking output,and an indicator circuit structured to indicate that the zone selectiveinterlocking input occurred at the first input or that the zoneselective interlocking output occurred at the second input.

In accordance with one aspect of the disclosed concept, a circuitinterrupter apparatus comprises: a circuit interrupter comprising:separable contacts, an operating mechanism structured to open and closethe separable contacts, and a trip mechanism cooperating with theoperating mechanism to trip open the separable contacts, the tripmechanism including a zone selective interlocking input and a zoneselective interlocking output; and a device comprising: a first inputelectrically interconnected with the zone selective interlocking input,a second input electrically interconnected with the zone selectiveinterlocking output, and an indicator circuit structured to indicatethat the zone selective interlocking input occurred at the first inputor that the zone selective interlocking output occurred at the secondinput.

As another aspect of the disclosed concept, a power distribution systemcomprises: a plurality of zones; and a plurality of circuit interrupterapparatus, each of the circuit interrupter apparatus being in one of thezones and comprising: separable contacts, an operating mechanismstructured to open and close the separable contacts, a trip mechanismcooperating with the operating mechanism to trip open the separablecontacts, the trip mechanism including a zone selective interlockinginput and a zone selective interlocking output, and a device comprising:a first input electrically interconnected with the zone selectiveinterlocking input, a second input electrically interconnected with thezone selective interlocking output, and an indicator circuit structuredto indicate that the zone selective interlocking input occurred at thefirst input or that the zone selective interlocking output occurred atthe second input, wherein the zone selective interlocking output of oneof the circuit interrupters in one of the zones is electricallyinterconnected with the zone selective interlocking input of another oneof the circuit interrupters in another upstream one of the zones.

The device of each of the circuit interrupters may be structured tocommunicate to a communication network a number of transitions and anumber of transition times of the zone selective interlocking input atthe first input and the zone selective interlocking output at the secondinput.

The communication network may include a processor structured to receivecommunications of the number of transitions and the number of transitiontimes from the device of each of the circuit interrupters.

The indicator circuit may comprise a reset circuit structured to removea first indication that the zone selective interlocking input occurredat the first input and a second indication that the zone selectiveinterlocking output occurred at the second input. The processor may befurther structured to provide at least one of: (1) displaying timing ofthe zone selective interlocking input at the first input and the zoneselective interlocking output at the second input of each of the circuitinterrupters; (2) actuating the reset circuit of each of the circuitinterrupters at about the same time; and (3) synchronizing the timing ofthe device of each of the circuit interrupters.

As another aspect of the disclosed concept, a zone selectiveinterlocking test apparatus comprises: a first input structured to beelectrically interconnected with a zone selective interlocking input ofa circuit interrupter; a second input structured to be electricallyinterconnected with a zone selective interlocking output of the circuitinterrupter; and an indicator circuit structured to indicate that thezone selective interlocking input occurred at the first input or thatthe zone selective interlocking output occurred at the second input.

As another aspect of the disclosed concept, a zone selectiveinterlocking test method is for a power distribution system including aplurality of zones. The method comprises: employing a plurality ofcircuit interrupters in the power distribution system, each of thecircuit interrupters being in one of the zones of the power distributionsystem and including a zone selective interlocking input and a zoneselective interlocking output; electrically interconnecting the zoneselective interlocking output of one of the circuit interrupters in oneof the zones with the zone selective interlocking input of another oneof the circuit interrupters in another upstream one of the zones;causing a trip of the one of the circuit interrupters; outputting thezone selective interlocking output of the one of the circuitinterrupters in the one of the zones to the zone selective interlockinginput of the another one of the circuit interrupters in the anotherupstream one of the zones; employing a device operatively associatedwith each of the circuit interrupters to monitor the zone selectiveinterlocking input and the zone selective interlocking output thereof,indicating from the device operatively associated with each of thecircuit interrupters whether the zone selective interlocking input andthe zone selective interlocking output thereof occurred; and checkingthe device operatively associated with each of the circuit interruptersto verify that the zone selective interlocking output of the one of thecircuit interrupters was received by a proper count of the circuitinterrupters and conversely was not received by any of the circuitinterrupters that should not have received the zone selectiveinterlocking output of the one of the circuit interrupters in the one ofthe zones.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of a power distribution systeminstallation designed for multiple power supplies with zone selectiveinterlocking.

FIG. 2 is a block diagram in schematic form of a circuit interrupterapparatus in accordance with embodiments of the disclosed concept.

FIGS. 3 and 4 are block diagrams in schematic form of indicator circuitsfor a zone selective interlocking test apparatus or a circuitinterrupter apparatus in accordance with other embodiments of thedisclosed concept.

FIG. 5 is a timing diagram of fault current versus a zone selectiveinterlocking output signal of a circuit interrupter.

FIG. 6 is a block diagram in schematic form of a power distributionsystem in accordance with other embodiments of the disclosed concept.

FIG. 7 is a flowchart of a zone selective interlocking test procedure inaccordance with another embodiment of the disclosed concept.

FIG. 8 is a timing diagram of zone selective interlocking input andoutput signals for the power distribution system of FIG. 6.

FIGS. 9 and 10 are isometric views of zone selective interlocking testdevices in accordance with other embodiments of the disclosed concept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As employed herein, the term “number” shall mean one or an integergreater than one (i.e., a plurality).

As employed herein, the term “processor” means a programmable analogand/or digital device that can store, retrieve, and process data; acomputer; a workstation; a personal computer; a microprocessor; amicrocontroller; a microcomputer; a central processing unit; a mainframecomputer; a mini-computer; a server; a networked processor; or anysuitable processing device or apparatus.

The disclosed concept is described in association with single-polecircuit breakers, although the disclosed concept is applicable tocircuit interrupters having any number of poles or phases in which zoneselective interlocking is applied to any fault, such as for example andwithout limitation, faults between phase and ground, between phases,and/or earth or ground faults.

Referring to FIG. 2, a circuit interrupter apparatus 10 includes acircuit interrupter 12 and a device 14, such as a zone selectiveinterlocking test apparatus. As is conventional, the circuit interrupter12 includes separable contacts 16, an operating mechanism 18 structuredto open and close the separable contacts 16, and a trip mechanism 20(e.g., without limitation, a trip unit) cooperating with the operatingmechanism 18 to trip open the separable contacts 16. The trip mechanism20 includes a zone selective interlocking input 22 and a zone selectiveinterlocking output 24. For example and without limitation, as isconventional, the trip unit decides when to trip, inputs a ZSI IN signalfrom the zone selective interlocking input 22, and outputs a ZSI OUTsignal to the zone selective interlocking output 24. The device 14includes a first input 26 electrically interconnected with the zoneselective interlocking input 22, a second input 28 electricallyinterconnected with the zone selective interlocking output 24, and anindicator circuit 30 structured to indicate at 32 that the zoneselective interlocking input 22 occurred at the first input 26 or thatthe zone selective interlocking output 24 occurred at the second input28.

Although the device 14 of FIG. 2 is shown as being internal to thecircuit interrupter apparatus 10, the function of this device can beexternal to a circuit interrupter, as is shown, for example, by theexample devices 116,118,120,122,124 of FIG. 6.

Example 1

FIG. 3 shows an example indicator circuit 34 including two set-resetflip-flops 36,38 and two corresponding indicator lights, such as lightemitting diodes (LEDs) 40,42. For example, whenever input 44 (ZSI IN/)is active low, flip-flop 36 is set, such that the LED 40 provides acorresponding ZSI IN signal indication. Whenever input 46 (ZSI OUT/) isactive low, flip-flop 38 is set, such that the LED 42 provides acorresponding ZSI OUT signal indication. Then, whenever reset pushbutton48 is depressed, both of the flip-flops 36,38 are reset, such that theLEDs 40,42 remove the corresponding ZSI IN and ZSI OUT signalindications.

Example 2

FIG. 4 shows another example indicator circuit 54 including a suitableprocessor, such as microcomputer (μC) 56 and two indicator lights, suchas LEDs 60,62. The μC 56 includes inputs P0,P1,P2 and outputs P3,P4,P5.For example, whenever input 64 (ZSI IN) is active high, μC output 65(P4) is set active low, such that the LED 60 provides a correspondingZSI IN signal indication. Whenever input 66 (ZSI OUT) is active high, μCoutput 67 (P3) is set active low, such that the LED 62 provides acorresponding ZSI OUT signal indication. Then, whenever reset pushbutton68 is depressed, both of the outputs 65,67 are reset inactive high, suchthat the LEDs 60,62 remove the corresponding ZSI IN and ZSI OUT signalindications.

Example 3

Although several example embodiments of the disclosed indicator circuits30,34,54 are disclosed, a suitable indicator circuit can employ any oneor more of transistor logic, logic gates, analog/digital logic, orprocessor-based implementations. For example, the logic in FIG. 3 isdone with digital logic flip-flops, although the μC 56 of FIG. 4 isessentially just as inexpensive and can provide relatively morefunctionality, as will be discussed.

Example 4

As shown in FIGS. 4 and 9, the indicator circuit 54 can also include anoptional display 70 driven by the μC 56. The μC 56 is structured tocooperate with the display 70 to display, for example, that a ZSI INsignal 61 (FIG. 9) occurred at the input 64 or that a ZSI OUT signal 63(FIG. 9) occurred at the other input 66. For example, the correspondingdevice 72 including the display 70, the reset pushbutton 68 and a ground(GND) reference 74 is shown in FIG. 9. For example, the display 70displays ZSI IN=YES for the ZSI IN signal 61 being active after a reset,and displays ZSI OUT=NONE for the ZSI OUT signal 63 being inactive aftera reset. Although not shown, it will be appreciated, for example, thatthe display 70 displays ZSI IN=NONE for the ZSI IN signal 61 beinginactive after a reset, and displays ZSI OUT=YES for the ZSI OUT signal63 being active after a reset. Although also not shown, it will furtherbe appreciated that both of the ZSI IN signal 61 and the ZSI OUT signal63 may be active or inactive after a reset, and that the display 70displays corresponding indicators of those signal states.

Example 5

Referring to FIGS. 3 and 10, a device 82 includes the LEDs 40,42, thereset pushbutton 48 and the ground (GND) reference 74 as shown in FIG.10. For example, the LED 40 is illuminated for the ZSI IN signal 45(FIG. 10) being active after a reset, and the LED 42 is extinguished forthe ZSI OUT signal 47 (FIG. 10) being inactive after a reset. Althoughnot shown, it will be appreciated, for example, that the LED 40 isextinguished for the ZSI IN signal 45 being inactive after a reset, andthe LED 42 is illuminated for the ZSI OUT signal 47 being active after areset. Although also not shown, it will further be appreciated that bothof the LEDs 40,42 may be active or inactive in response to correspondingstates of the signals 45,47 after a reset.

Example 6

Referring again to FIG. 4, the indicator circuit 54 can further includea status indicator light, such as LED 84, driven by μC output (P5) 86.The LED 84 can indicate, for example and without limitation, a status ofthe indicator circuit 54, such as the health of the μC 56.

Example 7

As shown in FIGS. 9 and 10, the disclosed devices 82,72 include a resetcircuit with a reset input formed by the respective reset buttons 48,68to allow the display 70 or LEDs 40,42 to be cleared or extinguished fora subsequent test, as will be explained, below, in connection with FIGS.6 and 7. The display 70 or the LEDs 40,42 of the respective devices72,82 indicate if those devices captured the ZSI IN signal 61,45 and/orthe ZSI OUT signal 63,47. The reset buttons 68,48 provide a resetcircuit structured to remove an indication that the ZSI IN signal 61,45occurred at the inputs 64,44, and an indication that the ZSI OUT signal63,47 occurred at the inputs 66,46.

Example 8

As shown in FIGS. 3 and 4, a power source 88 for the indicator circuits34,54 for the devices 72,82 of FIGS. 9 and 10 can be any suitable powersource, such as a battery, a power source of a trip mechanism (e.g., oftrip mechanism 20 of FIG. 2) or an external power source.

Example 9

The processor 56 of FIG. 4 preferably includes suitable diagnostics toshow that a number of different variations of the signals at inputs ZSIIN 64 and ZSI OUT 66 were observed. FIG. 5 shows a timing diagram offault current 90 versus the ZSI OUT signal 63 of FIG. 9. At 92, the ZSIOUT signal 63 is asserted in response to the detection of the faultcurrent 94. Here, the processor 56 is structured to determine if the ZSIOUT signal 63 occurred for less than a predetermined time 96 (e.g.,without limitation, about 10 ms) and to cooperate with the display 70 todisplay (e.g., “ZSI OUT=10 ms NO TRIP”) that the ZSI OUT signal 63occurred at the ZSI OUT input 66 (FIG. 4) and was not associated with acorresponding trip of a circuit interrupter. For example, the examplefault current 94 is associated with only a positive half-cycle (e.g.,8.33 ms at 60 Hz) of the alternating current waveform. Since the faultcurrent 94 did not persist, the trip mechanism (e.g., 20 of FIG. 2) didnot determine a trip condition and the ZSI OUT signal 63 was cleared.

Conversely, at 98, the ZSI OUT signal 63 is asserted in response to thedetection of the fault current 100, which persists for a plurality ofpositive and negative half-cycles of the alternating current waveform.Hence, the processor 56 determines that the ZSI OUT signal 63 occurredfor greater than the predetermined time 96 and cooperates with thedisplay 70 to display (e.g., “ZSI OUT=YES”) since the ZSI OUT signal 63occurred at the ZSI OUT input 66 (FIG. 4) and was associated with acorresponding trip of the circuit interrupter.

Hence, metering the time that one or both of the ZSI IN signal 61 andthe ZSI OUT signal 63 are active can be a valuable diagnostic tool.Additional examples of this are discussed, below, in connection withFIG. 8 and Examples 16-18.

Example 10

Referring to FIG. 6, a power distribution system 102 includes aplurality of circuit interrupter zones 104, such as ZONE 1, ZONE 2 andZONE 3; and a plurality of circuit interrupters, such as circuitbreakers CB1 106, CB2 108, CB3 110, CB4 112 and CB5 114. Each of theexample circuit breakers 106,108,110,112,114 is in one of the zones 104.For example, circuit breakers CB1 106 and CB2 108 are in ZONE 3, circuitbreakers CB3 110 and CB4 112 are in ZONE 2, and circuit breaker CB5 114is in ZONE 1. Each of the example circuit breakers 106,108,110,112,114is operatively associated with a corresponding one of the respectivedevices M1 116, M2 118, M3 120, M4 122, M5 124, which are the same as orsimilar to one of the devices 72,82 of FIGS. 9 and 10. Although thedevices 116,118,120,122,124 are shown as being external to the circuitbreakers 106,108,110,112,114, respectively, the function of thesedevices may be internal (see, for example, device 14 of FIG. 2) to suchcircuit breakers. As shown, for example, with circuit breaker CB5 114and device M5 124, and as was discussed above in connection with FIG. 2,the device M5 124 includes the first input (ZSI IN) 26 electricallyinterconnected with the zone selective interlocking input (ZSI IN) 22 ofthe circuit breaker CB5 114, and the second input (ZSI OUT) 28electrically interconnected with the zone selective interlocking output(ZSI OUT) 24 of the circuit breaker CB5 114. As shown, for example, withcircuit breaker CB3 110 and circuit breaker CB5 114, the ZSI OUT 24 ofCB3 110 in ZONE 2 is electrically interconnected with the ZSI IN 22 ofCB5 114 of the adjacent upstream ZONE 1.

Example 11

As shown in FIG. 6, the devices 116,118,120,122,124 preferably include atransceiver 126 (e.g., without limitation, a wireless transceiver, asshown; a wired transceiver) structured to communicate to a communicationnetwork 127 (e.g., without limitation, a wireless communication network,such as a wireless local area network, as shown; a wired communicationnetwork) a number of transitions and a number of transition times of thezone selective interlocking signals at the inputs 26,28. For example,the processor 56 of FIG. 4 can count the number of low-to-hightransitions of the inputs 26,28 and/or the number of high-to-lowtransitions of the inputs 26,28, along with the periods of time that theinputs 26,28 are high and/or low, and communicate the same using thetransceiver 126.

Example 12

The information from Example 11 can be communicated to a suitableprocessor 128 over the communication network 127. The processor 128 isstructured to receive communications of the number of transitions andthe number of transition times from the devices 116,118,120,122,124 forsuitable processing and analysis.

Example 13

Further to Examples 11 and 12, the processor 56 of FIG. 4 can bestructured to receive a reset signal 130 and/or a time synchronizationsignal 132 through its transceiver 126 from the processor 128 of FIG. 6over the communication network 127. When the reset signal 130 isreceived, the processor 56 of FIG. 4 of each of the devices116,118,120,122,124 takes the same action as if the manual resetpushbutton 68 was pressed. Hence, all of these devices, which can bephysically separated, can be reset from a single location. The timesynchronization signal 132 preferably resets a timer (not shown) or setsa real time clock (not shown) of the processor 56 of each of the devices116,118,120,122,124, in order that real or relative times can beassigned to the transition times of the zone selective interlockingsignals at the inputs 26,28. Again, this action can be taken from asingle location at the processor 128. Preferably, the processor 128 isstructured to provide at least one of: (1) receiving and displaying ondisplay 129 timing of the zone selective interlocking inputs 26,28 fromeach of the devices 116,118,120,122,124 for each of the respectivecircuit breakers 106,108,110,112,114; (2) actuating the reset circuit ofthe processor 56 of FIG. 4 of each of the devices 116,118,120,122,124 atabout the same time; and (3) synchronizing the timing of each of thedevices 116,118,120,122,124. For example, this can enable all of thedevices 116,118,120,122,124 to be connected together to show the timingof the various ZSI signals (e.g., which occurred first, second, thirdand so forth), with the devices being reset all at once, and the devicesbeing time synchronized to show the real or relative times of the signaltransitions.

Example 14

As shown in FIG. 6, steering diodes 130 are preferably employed toprevent an improper back feed to the ZSI OUT 28 input of a downstreamdevice from an upstream circuit breaker or device or to the ZSI OUT 28input of a device from another circuit breaker or device in the samezone (e.g., device M4 122 should not see the ZSI OUT signal from CB3110; device M3 120 should not see the ZSI OUT signal from CB4 112). Forexample, as shown in ZONE 3, the blocking diode 130 is electricallyconnected between the ZSI IN input 22 of CB3 110 in ZONE 2 and the ZSIOUT output 24 of CB1 106 in ZONE 3. Similarly, as shown in ZONE 2, theblocking diode 130 is electrically connected between the ZSI IN input 22of CB5 114 in ZONE 1 and the ZSI OUT output 24 of CB3 110 in ZONE 2.

Example 15

When a switchgear system is wired for zone selective interlocking (ZSI)(e.g., as shown in FIG. 6), physically, there are cells of circuitbreakers spread throughout the switchgear. ZSI wires for the various ZSIsignals are routed between the circuit breakers (e.g.,106,108,110,112,114) according to a wiring diagram designed byengineers. The problem with ZSI input and ZSI output signals is thatthey come out of the circuit breakers relatively very fast and last fora relatively short time. These ZSI signals only appear on or at thecircuit breaker trip unit for less than about 100 ms. Hence, suitablehigh speed devices (e.g., 116,118,120,122,124) capture these signals, inorder to know that they appeared at the proper circuit breakers (e.g.,106,108,110,112,114) at the right times. The disclosed devices arecoupled to the ZSI input 22 and ZSI output 24 with a common ground(e.g., GND 74 of FIGS. 9 and 10) for each circuit breaker. The discloseddevices look at the ZSI input and ZSI output signals to capture thosesignals and indicate and hold that indication that the signals appeared.Preferably, the disclosed devices have a display (e.g., 70 of FIG. 4) orother suitable indicator (e.g., 40,42 of FIG. 3) that allows the user(e.g., customer; person who builds switchgear, panelboard, switch board,or other ZSI system or devices) to determine that the ZSI wiring wasdone correctly and that the proper ZSI signals were received or were notreceived.

The following describes one example of how to initiate a trip signalfrom a trip unit to force the trip unit to send out a ZSI OUT signal,such as 63 or 47 of FIGS. 9 and 10, in order that the power distributionsystem can be tested. Large current signals cannot easily be applied toa bus system to test the system. The ZSI signals only come out when theshort delay protection is applied by the trip unit. This short delayprotection is in the range of two to ten times the continuous ratedcurrent of the corresponding circuit breaker. For a relatively largecircuit breaker, this could be, for example, 32,000 amps. This is toolarge to apply to the whole system, is too dangerous and is notpractical. When the circuit breakers are tested with a tester, usually asecondary current is applied to one and only one circuit breaker at atime. This makes it difficult to see if an intended circuit breakerupstream has seen the ZSI signals. Also, in the event of a wiring error,it is difficult to see if a particular circuit breaker improperly sawthe ZSI signals from the tested circuit breaker.

As shown in FIG. 6, the disclosed devices 116,118,120,122,124 couple tothe ZSI IN input 22 and the ZSI OUT output 24 to capture the ZSI signalsin and out, in order to see if the ZSI wiring is correct. The devices116,118,120,122,124 are added to or included within each circuit breakerin the power distribution system so that all the circuit breakers arecovered. A secondary test current is applied to a circuit breaker ofinterest at the Short Delay Pick-up level. After this circuit breakertrips, the devices 116,118,120,122,124 are checked (e.g., locally ateach device; globally at the processor 128) to see if the ZSI OUT signalfrom the tested circuit breaker got to the proper number of circuitbreakers or conversely did not go to any circuit breakers that shouldnot have received that ZSI OUT signal. Then, all of the devices116,118,120,122,124 are reset or cleared (e.g., locally at each deviceusing the reset pushbutton 48 or 68 of FIGS. 3 and 4; globally at theprocessor 128 using the reset signal 130) and the process is repeatedwith another circuit breaker being tested with the secondary testcurrent.

Referring to FIG. 7, a ZSI test procedure 140 is shown for a powerdistribution system (e.g., 102 of FIG. 6) including a plurality of zones(e.g., without limitation, as shown by the three zones 104 of FIG. 6).At 142, a plurality of circuit interrupters (e.g., circuit breakers106,108,110,112,114) are employed in the power distribution system, eachof the circuit interrupters being in one of the zones of the powerdistribution system and including a ZSI input (e.g., 22) and a ZSIoutput (e.g., 24). At 144, the ZSI OUT output 24 of one of the circuitinterrupters (e.g., CB3 110) in one of the zones (e.g., ZONE 2) iselectrically interconnected with the ZSI IN input 22 of another one ofthe circuit interrupters (e.g., CB5 114) in another upstream one of thezones (e.g., ZONE 1). Next, at 146, a trip is caused (e.g., as wasdiscussed above) of such one of the circuit interrupters (e.g., CB3110). Then, at 148, the ZSI OUT output 24 of such one of the circuitinterrupters (e.g., CB3 110) in such one of the zones (e.g., ZONE 2) isoutput to the ZSI IN input 22 of the other one of the circuitinterrupters (e.g., CB5 114) in the other upstream one of the zones(e.g., ZONE 1). Next, at 150, devices (e.g., 116,118,120,122,124) areoperatively associated with each of the circuit interrupters (e.g.,106,108,110,112,114) to monitor the ZSI IN input 22 and the ZSI OUToutput 24 thereof. Then, at 152, the devices operatively associated witheach of the circuit interrupters indicate whether the ZSI IN input 22and the ZSI OUT output 24 thereof occurred. Finally, at 154, the devicesoperatively associated with each of the circuit interrupters are checkedto verify that the ZSI OUT output 24 of the one of the circuitinterrupters (e.g., CB3 110) was received by a proper count (e.g., acount of two example CBs 110,114 in this example) of the circuitinterrupters and conversely was not received by any of the circuitinterrupters (e.g., the other three example CBs 106,108,112 in thisexample) that should not have received the ZSI OUT output of that one ofthe circuit interrupters (e.g., CB3 110).

As was discussed above in connection with FIGS. 4 and 9, the display 70of the devices (e.g., 116,118,120,122,124) operatively associated witheach of the circuit interrupters (e.g., 106,108,110,112,114) indicatefollowing a reset of the devices the occurrence or non-occurrence of theZSI OUT output 24 and the ZSI IN input 22 thereof.

In turn, after the devices are reset (e.g., as was discussed above inconnection with FIGS. 3, 4 or Example 13), a trip is caused of anotherone of the circuit interrupters, as at 146, and even steps 148 to 154 ofFIG. 7 are repeated to check the corresponding ZSI wiring and logic.

It will be appreciated that this ZSI test procedure 140 can be performedusing the example devices 116,118,120,122,124 with or without theprocessor 128.

Example 16

Referring to FIG. 8, a timing diagram shows example ZSI OUT and ZSI INsignals monitored by the devices M1 116, M3 120 and M5 124 of FIG. 6.Although these are described using the M1,M3,M5 references of thedevices, they could alternatively be described using the respectiveCB1,CB3,CB5 references of the corresponding circuit interrupters. Attransition 160, a fault is detected by CB1 106 and M1 ZSI OUT is set. Atinactive signal 162, M1 ZSI IN is inactive, since there is no downstreamcircuit breaker. At transition 164, M3 ZSI IN to CB3 110 follows M1 ZSIOUT. Then, at transition 166, CB3 110 responsively sets M3 ZSI OUT. Attransition 168, M5 ZSI IN to CB5 114 follows M3 ZSI OUT. Then, attransition 170, CB5 114 responsively sets M5 ZSI OUT.

M1 ZSI OUT persists until, at transition 172, CB1 106 opens and clearsthe fault that it detected at 160. M1 ZSI IN has remained inactive,since there is no downstream circuit breaker. At transition 174, M3 ZSIIN to CB3 110 follows M1 ZSI OUT and goes inactive. Then, at transition176, since the fault current has been interrupted by CB1 106, CB3 110responsively clears M3 ZSI OUT. At transition 178, M5 ZSI IN to CB5 114follows M3 ZSI OUT and goes inactive. Then, at transition 180, since thefault current has been interrupted by CB1 106, CB5 114 responsivelyclears M5 ZSI OUT.

For example, between transition 160 and transition 172, the processor 56of FIG. 4 of the device M1 116 is structured to determine if the ZSI OUToutput 24 (its ZSI OUT input 28) occurred for greater than apredetermined time (e.g., without limitation, 50 ms) and to cooperatewith the display 70 to display (e.g., ZSI OUT=50 ms TRIP) in order toindicate that the ZSI OUT output 24 occurred at its ZSI OUT input 28 andwas associated with a trip of the corresponding circuit interrupter CB1106.

Example 17

For example, between transitions 160, 164 and 168 and respectivetransitions 172, 174 and 178, the processor 56 of FIG. 4 of the devicesM1 116, M3 120 and M5 124 is structured to determine if the ZSI IN input22 occurred in conjunction with the ZSI OUT output 24 and to cooperatewith the display 70 to display that the ZSI OUT output 24 occurred atthe device's ZSI OUT input 28 and was associated with a trip of one of:(1) the circuit interrupter CB1 106 (since device M1 116 sees ZSI OUT=55ms TRIP; ZSI IN=off; thus, there is no circuit interrupter downstream ofCB1 106); (2) the adjacent, downstream circuit interrupter CB1 106(since device M3 120 sees ZSI OUT=60 ms TRIP; ZSI IN=on 55 ms; thus,there is the adjacent, downstream circuit breaker CB1 106 in theadjacent ZONE 3 downstream of CB3 110, which is in the adjacent upstreamZONE 2); and (3) the non-adjacent, downstream circuit interrupter CB1106 (since device M5 124 sees ZSI OUT=60 ms TRIP; ZSI IN=on 60 ms; thus,there is the non-adjacent, downstream circuit breaker CB1 106 in thenon-adjacent ZONE 3 downstream of CB5 114, which is in the non-adjacentupstream ZONE 1).

Example 18

As can be seen from the above Examples 16 and 17, the indicator circuit54 of FIG. 4 is preferably structured to analyze timing of the ZSI INinput 22 at the ZSI IN input 26 and the ZSI OUT output 24 at the ZSI OUTinput 28.

Example 19

Although separable contacts 16 are disclosed, suitable solid stateseparable contacts may be employed. For example, the disclosed circuitinterrupter 10 includes a suitable circuit interrupter mechanism, suchas the separable contacts 16 that are opened and closed by the operatingmechanism 18, although the disclosed concept is applicable to a widerange of circuit interruption mechanisms (e.g., without limitation,solid state or FET switches; contactor contacts) and/or solid statebased control/protection devices (e.g., without limitation, drives;soft-starters).

While specific embodiments of the disclosed concept have been describedin detail, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure.Accordingly, the particular arrangements disclosed are meant to beillustrative only and not limiting as to the scope of the disclosedconcept which is to be given the full breadth of the claims appended andany and all equivalents thereof.

1. A power distribution system comprising: a plurality of zones; and aplurality of circuit interrupter apparatus, each of said circuitinterrupter apparatus being in one of said zones and comprising:separable contacts, an operating mechanism structured to open and closesaid separable contacts, a trip mechanism cooperating with saidoperating mechanism to trip open said separable contacts, said tripmechanism including a zone selective interlocking input and a zoneselective interlocking output, and a device comprising: a first inputelectrically interconnected with said zone selective interlocking input,a second input electrically interconnected with said zone selectiveinterlocking output, and an indicator circuit structured to indicatethat said zone selective interlocking input occurred at said first inputor that said zone selective interlocking output occurred at said secondinput, wherein the zone selective interlocking output of one of saidcircuit interrupters in one of said zones is electrically interconnectedwith the zone selective interlocking input of another one of saidcircuit interrupters in another upstream one of said zones, wherein thedevice of each of said circuit interrupters is structured to communicateto a communication network a number of transitions and a number oftransition times of said zone selective interlocking input at said firstinput and said zone selective interlocking output at said second input.2. The power distribution system of claim 1 wherein said communicationnetwork includes a processor structured to receive communications ofsaid number of transitions and said number of transition times from thedevice of each of said circuit interrupters.
 3. The power distributionsystem of claim 2 wherein said indicator circuit comprises a resetcircuit structured to remove a first indication that said zone selectiveinterlocking input occurred at said first input and a second indicationthat said zone selective interlocking output occurred at said secondinput; and wherein said processor is further structured to provide atleast one of: (1) displaying timing of the zone selective interlockinginput at the first input and the zone selective interlocking output atthe second input of each of said circuit interrupters; (2) actuating thereset circuit of each of said circuit interrupters at about the sametime; and (3) synchronizing the timing of the device of each of saidcircuit interrupters.
 4. A power distribution system comprising: aplurality of zones; and a plurality of circuit interrupter apparatus,each of said circuit interrupter apparatus being in one of said zonesand comprising: separable contacts, an operating mechanism structured toopen and close said separable contacts, a trip mechanism cooperatingwith said operating mechanism to trip open said separable contacts, saidtrip mechanism including a zone selective interlocking input and a zoneselective interlocking output, and a device comprising: a first inputelectrically interconnected with said zone selective interlocking input,a second input electrically interconnected with said zone selectiveinterlocking output, and an indicator circuit structured to indicatethat said zone selective interlocking input occurred at said first inputor that said zone selective interlocking output occurred at said secondinput, wherein the zone selective interlocking output of one of saidcircuit interrupters in one of said zones is electrically interconnectedwith the zone selective interlocking input of another one of saidcircuit interrupters in another upstream one of said zones, wherein thezone selective interlocking output of said one of said circuitinterrupters in said one of said zones is the zone selectiveinterlocking output of a first one of said circuit interrupters in asecond one of said zones; wherein the zone selective interlocking inputof said another one of said circuit interrupters in said anotherupstream one of said zones is the zone selective interlocking input of asecond one of said circuit interrupters in a first upstream one of saidzones; wherein the zone selective interlocking output of a third one ofsaid circuit interrupters in the second one of said zones is alsoelectrically interconnected with the zone selective interlocking inputof said second one of said circuit interrupters in said first upstreamone of said zones; wherein a first blocking diode is electricallyconnected between the zone selective interlocking input of the secondone of said circuit interrupters in the first upstream one of said zonesand the zone selective interlocking output of the first one of saidcircuit interrupters in the second one of said zones; and wherein asecond blocking diode is electrically connected between the zoneselective interlocking input of the second one of said circuitinterrupters in the first upstream one of said zones and the zoneselective interlocking output of the third one of said circuitinterrupters in the second one of said zones.
 5. A zone selectiveinterlocking test method for a power distribution system including aplurality of zones, said method comprising: employing a plurality ofcircuit interrupters in said power distribution system, each of saidcircuit interrupters being in one of said zones of said powerdistribution system and including a zone selective interlocking inputand a zone selective interlocking output; electrically interconnectingthe zone selective interlocking output of one of said circuitinterrupters in one of said zones with the zone selective interlockinginput of another one of said circuit interrupters in another upstreamone of said zones; causing a trip of said one of said circuitinterrupters; outputting the zone selective interlocking output of saidone of said circuit interrupters in said one of said zones to the zoneselective interlocking input of said another one of said circuitinterrupters in said another upstream one of said zones; employing adevice operatively associated with each of said circuit interrupters tomonitor the zone selective interlocking input and the zone selectiveinterlocking output thereof; indicating from the device operativelyassociated with each of said circuit interrupters whether the zoneselective interlocking input and the zone selective interlocking outputthereof occurred; and checking the device operatively associated witheach of said circuit interrupters to verify that the zone selectiveinterlocking output of said one of said circuit interrupters wasreceived by a proper count of said circuit interrupters and converselywas not received by any of said circuit interrupters that should nothave received the zone selective interlocking output of said one of saidcircuit interrupters in said one of said zones.
 6. The zone selectiveinterlocking test method of claim 5 further comprising employing adisplay of the device operatively associated with each of said circuitinterrupters to indicate the occurrence or non-occurrence of the zoneselective interlocking output and the zone selective interlocking inputthereof.
 7. The zone selective interlocking test method of claim 6further comprising resetting the device operatively associated with eachof said circuit interrupters; causing a trip of another one of saidcircuit interrupters; outputting the zone selective interlocking outputof said another one of said circuit interrupters; employing the deviceoperatively associated with each of said circuit interrupters to monitorthe zone selective interlocking input and the zone selectiveinterlocking output thereof; indicating from the device operativelyassociated with each of said circuit interrupters whether the zoneselective interlocking input and the zone selective interlocking outputthereof occurred; and checking the device operatively associated witheach of said circuit interrupters to verify that the zone selectiveinterlocking output of said another one of said circuit interrupters wasreceived by a proper count of said circuit interrupters and converselywas not received by any of said circuit interrupters that should nothave received the zone selective interlocking output of said another oneof said circuit interrupters.